The Fifth Gordon Research Conference on Motile and Contractile Systems will provide an informal forum for recent advances and new directions in this active field. The focus of this conference will be on the actin-based and microtubule-based cytoskeletal components, their structures and important domains, their regulators and their motors. These topics are relevant to many fields including neurodegenerative and musculoskeletal disease, respiratory disease, development, transformation, oncogenesis as well as the normal functioning of the organism. The conference will include approximately 30 formal presentations by invited speakers in 9 lecture-discussion sessions with a major emphasis on discussion by all participants. The other participants, including junior scientists in particular, will be encouraged to present posters of their work and 2 formal poster Sessions will be scheduled. This basic format has worked well in the previous 4 conferences, and we plan to continue emphasizing a minimum of formal presentations in order to maximize discussion and exchange of new unpublished results and techniques. The conference will begin with a session on (l) The structure of actin and associated proteins. This will be followed by sessions on (2) the structure/function relationships of microtubule associated motors; (3) the behavioral consequences of motor function; and (4) mutant analysis of motor function. The next session, (5) heterologous liaisons, will highlight important new and previously unexpected interactions between cytoskeletal proteins and other organelles. Sessions 6 and 7 will compare the regulation of actin and tubulin polymerization in vitro and in vivo. The conference will close with (8) signal transduction and cell motility and (9) cell division. Throughout the meeting actin and tubulin based themes will be interwoven to encourage direct comparison and new insights.